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5,500 | The Special Sensor Microwave/Imager (SSM/I) is a seven-channel, four-frequency, linearly polarized passive microwave radiometer system. It is flown on board the United States Air Force Defense Meteorological Satellite Program (DMSP) Block 5D-2 satellites. The instrument measures surface/atmospheric microwave brightness temperatures (TBs) at 19 | Special sensor microwave/imager |
5,501 | The spectral G-Index is a variable that was developed to quantify the amount of short wavelength light in a visible light source relative to its visible emission (it is a measure of the amount of blue light per lumen). The smaller the G-index, the more blue, violet, or ultraviolet light a lamp emits relative to its total output. It is used in order to select outdoor lamps that minimize skyglow and ecological light pollution | Spectral G-index |
5,502 | In radiometry, photometry, and color science, a spectral power distribution (SPD) measurement describes the power per unit area per unit wavelength of an illumination (radiant exitance). More generally, the term spectral power distribution can refer to the concentration, as a function of wavelength, of any radiometric or photometric quantity (e. g | Spectral power distribution |
5,503 | In radiometry, spectral radiance or specific intensity is the radiance of a surface per unit frequency or wavelength, depending on whether the spectrum is taken as a function of frequency or of wavelength. The SI unit of spectral radiance in frequency is the watt per steradian per square metre per hertz (W·sr−1·m−2·Hz−1) and that of spectral radiance in wavelength is the watt per steradian per square metre per metre (W·sr−1·m−3)—commonly the watt per steradian per square metre per nanometre (W·sr−1·m−2·nm−1). The microflick is also used to measure spectral radiance in some fields | Spectral radiance |
5,504 | Spectral sensitivity is the relative efficiency of detection, of light or other signal, as a function of the frequency or wavelength of the signal.
In visual neuroscience, spectral sensitivity is used to describe the different characteristics of the photopigments in the rod cells and cone cells in the retina of the eye. It is known that the rod cells are more suited to scotopic vision and cone cells to photopic vision, and that they differ in their sensitivity to different wavelengths of light | Spectral sensitivity |
5,505 | Spectrophotometry is a branch of electromagnetic spectroscopy concerned with the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength. Spectrophotometry uses photometers, known as spectrophotometers, that can measure the intensity of a light beam at different wavelengths. Although spectrophotometry is most commonly applied to ultraviolet, visible, and infrared radiation, modern spectrophotometers can interrogate wide swaths of the electromagnetic spectrum, including x-ray, ultraviolet, visible, infrared, and/or microwave wavelengths | Spectrophotometry |
5,506 | The Special Sensor Microwave Imager / Sounder (SSMIS) is a 24-channel, 21-frequency, linearly polarized passive microwave radiometer system. The instrument is flown on board the United States Air Force Defense Meteorological Satellite Program (DMSP) F-16, F-17, F-18 and F-19 satellites, which were launched in October 2003, November 2006, October 2009, and April 2014, respectively. It is the successor to the Special Sensor Microwave/Imager (SSM/I) | SSMIS |
5,507 | The Stokes parameters are a set of values that describe the polarization state of electromagnetic radiation. They were defined by George Gabriel Stokes in 1852, as a mathematically convenient alternative to the more common description of incoherent or partially polarized radiation in terms of its total intensity (I), (fractional) degree of polarization (p), and the shape parameters of the polarization ellipse. The effect of an optical system on the polarization of light can be determined by constructing the Stokes vector for the input light and applying Mueller calculus, to obtain the Stokes vector of the light leaving the system | Stokes parameters |
5,508 | The superconducting nanowire single-photon detector (SNSPD or SSPD) is a type of optical and near-infrared single-photon detector based on a current-biased superconducting nanowire. It was first developed by scientists at Moscow State Pedagogical University and at the University of Rochester in 2001. The first fully operational prototype was demonstrated in 2005 by the National Institute of Standards and Technology (Boulder), and BBN Technologies as part of the DARPA Quantum Network | Superconducting nanowire single-photon detector |
5,509 | TMOS is a new type of thermal sensor consisting in a micromachined thermally isolated transistor fabricated using CMOS-SOI(Silicon on Insulator) MEMS(Micro electro-mechanical system) technology. It has been developed in the last decade by the Technion - Israel Institute of Technology. A thermal sensor is a device able to detect the thermal radiation emitted by an object located in the FOV(Field Of View) of the sensor | T-MOS thermal sensor |
5,510 | Thin filament pyrometry (TFP) is an optical method used to measure temperatures. It involves the placement of a thin filament in a hot gas stream. Radiative emissions from the filament can be correlated with filament temperature | Thin filament pyrometry |
5,511 | A transition-edge sensor (TES) is a type of cryogenic energy sensor or cryogenic particle detector that exploits the strongly temperature-dependent resistance of the superconducting phase transition.
History
The first demonstrations of the superconducting transition's measurement potential appeared in the 1940s, 30 years after Onnes's discovery of superconductivity. D | Transition-edge sensor |
5,512 | Transmittance of the surface of a material is its effectiveness in transmitting radiant energy. It is the fraction of incident electromagnetic power that is transmitted through a sample, in contrast to the transmission coefficient, which is the ratio of the transmitted to incident electric field. Internal transmittance refers to energy loss by absorption, whereas (total) transmittance is that due to absorption, scattering, reflection, etc | Transmittance |
5,513 | In spectroscopy and radiometry, vector radiative transfer (VRT) is a method of modelling the propagation of polarized electromagnetic radiation in low density media. In contrast to scalar radiative transfer (RT), which models only the first Stokes component, the intensity, VRT models all four components through vector methods.
For a single frequency,
ν
{\displaystyle \nu }
, the VRT equation for a scattering media can be written as follows:
d
I
→
(
n
^
,
ν
)
d
s
=
−
K
I
→
+
a
→
B
(
ν
,
T
)
+
∫
4
π
Z
(
n
^
,
n
^
′
,
ν
)
I
→
d
n
^
′
{\displaystyle {\frac {\mathrm {d} {\vec {I}}({\hat {n}},\nu )}{\mathrm {d} s}}=-\mathbf {K} {\vec {I}}+{\vec {a}}B(\nu ,T)+\int _{4\pi }\mathbf {Z} ({\hat {n}},{\hat {n}}^{\prime },\nu ){\vec {I}}\mathrm {d} {\hat {n}}^{\prime }}
where s is the path,
n
^
{\displaystyle {\hat {n}}}
is the propagation vector, K is the extinction matrix,
a
→
{\displaystyle {\vec {a}}}
is the absorption vector, B is the Planck function and Z is the scattering phase matrix | Vector radiative transfer |
5,514 | This is a list of satellites in geosynchronous orbit (GSO). These satellites are commonly used for communication purposes, such as radio and television networks, back-haul, and direct broadcast. Traditional global navigation systems do not use geosynchronous satellites, but some SBAS navigation satellites do | List of satellites in geosynchronous orbit |
5,515 | An antenna tracking system tracks a primary antenna to follow a moving signal source, such as a communication satellite. A secondary antenna has a greater beam width than the primary antenna and receives the same tracking signal from the satellite. The primary antenna is tracked according to a predetermined search pattern which causes a variation in the signal amplitude depending upon the relative location of the satellite and the antenna position | Antenna tracking system |
5,516 | The Automatic Picture Transmission (APT) system is an analog image transmission system developed for use on weather satellites. It was introduced in the 1960s and over four decades has provided image data to relatively low-cost user stations at locations in most countries of the world. A user station anywhere in the world can receive local data at least twice a day from each satellite as it passes nearly overhead | Automatic picture transmission |
5,517 | Automatic Tracking Satellite Dishes are satellite dishes used while a vehicle, boat or ship is in motion. Automatic tracking satellite dishes utilize gyroscopes, GPS position sensors, and uses unique satellite identification data and an integrated DVB decoder to aid in identification of the satellite that it is pointing at.
The dishes consist usually of stepper motors to drive and aim the dish, gyroscopes to detect changes in position while the vehicle is in motion, a parabolic reflector, low-noise block converter, and control unit | Automatic-tracking satellite dish |
5,518 | Basic Interoperable Scrambling System, usually known as BISS, is a satellite signal scrambling system developed by the European Broadcasting Union and a consortium of hardware manufacturers.
Prior to its development, "ad hoc" or "occasional use" satellite news feeds were transmitted either using proprietary encryption methods (e. g | Basic Interoperable Scrambling System |
5,519 | A block upconverter (BUC) is used in the transmission (uplink) of satellite signals. It converts a band of frequencies from a lower frequency to a higher frequency. Modern BUCs convert from the L band to Ku band, C band and Ka band | Block upconverter |
5,520 | This is a list of satellites in geosynchronous orbit (GSO). These satellites are commonly used for communication purposes, such as radio and television networks, back-haul, and direct broadcast. Traditional global navigation systems do not use geosynchronous satellites, but some SBAS navigation satellites do | List of satellites in geosynchronous orbit |
5,521 | The C band is a designation by the Institute of Electrical and Electronics Engineers (IEEE) for a portion of the electromagnetic spectrum in the microwave range of frequencies ranging from 4. 0 to 8. 0 gigahertz (GHz) | C band (IEEE) |
5,522 | Co-location is the placing of two or more geostationary communications satellites in orbit, in close proximity so that to reception equipment on the ground they 'appear' to occupy a single orbital position. The technique as applied to a group of TV satellites from a single operator was pioneered by SES with the Astra satellites at 19. 2°E | Co-location (satellite) |
5,523 | Commercial use of space is the provision of goods or services of commercial value by using equipment sent into Earth orbit or outer space. This phenomenon – aka Space Economy (or New Space Economy) – is accelerating cross-sector innovation processes combining the most advanced space and digital technologies to develop a broad portfolio of space-based services. The use of space technologies and of the data they collect, combined with the most advanced enabling digital technologies is generating a multitude of business opportunities that include the development of new products and services all the way to the creation of new business models, and the reconfiguration of value networks and relationships between companies | Commercial use of space |
5,524 | This is a list of all companies currently operating at least one commercial communication satellite or currently has one on order.
Global Top 20
The World Teleport Association publishes lists of companies based on revenues from all customized communications sources and includes operators of teleports and satellite fleets. In order from largest to smallest, the Global Top 20 of 2021 were:
SES (Luxembourg)
Intelsat S | List of communication satellite companies |
5,525 | A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. Communications satellites are used for television, telephone, radio, internet, and military applications. Many communications satellites are in geostationary orbit 22,300 miles (35,900 km) above the equator, so that the satellite appears stationary at the same point in the sky; therefore the satellite dish antennas of ground stations can be aimed permanently at that spot and do not have to move to track the satellite | Communications satellite |
5,526 | Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location. The signals are received via an outdoor parabolic antenna commonly referred to as a satellite dish and a low-noise block downconverter.
A satellite receiver then decodes the desired television program for viewing on a television set | Satellite television |
5,527 | In a telecommunications network, a link is a communication channel that connects two or more devices for the purpose of data transmission. The link may be a dedicated physical link or a virtual circuit that uses one or more physical links or shares a physical link with other telecommunications links.
A telecommunications link is generally based on one of several types of information transmission paths such as those provided by communication satellites, terrestrial radio communications infrastructure and computer networks to connect two or more points | Telecommunications link |
5,528 | DVB-RCS is an acronym for Digital Video Broadcasting - Return Channel via Satellite or (Return channel over system). It is a specification for an interactive on-demand multimedia satellite communication system formulated in 1999 by the DVB consortium.
Chronology
The 5th revision of the DVB-RCS standard was completed in 2008 | DVB-RCS |
5,529 | Digital Video Broadcasting – Satellite (DVB-S) is the original DVB standard for satellite television and dates from 1995, in its first release, while development lasted from 1993 to 1997. The first commercial applications were by Star TV in Asia and Galaxy in Australia, enabling digitally broadcast, satellite-delivered television to the public. DVB-S was the first DVB standard for satellite, defining the framing structure, channel coding and modulation for 11/12 GHz satellite services | DVB-S |
5,530 | Digital Video Broadcasting - Satellite - Second Generation (DVB-S2) is a digital television broadcast standard that has been designed as a successor for the popular DVB-S system. It was developed in 2003 by the Digital Video Broadcasting Project, an international industry consortium, and ratified by ETSI (EN 302307) in March 2005. The standard is based on, and improves upon DVB-S and the electronic news-gathering (or Digital Satellite News Gathering) system, used by mobile units for sending sounds and images from remote locations worldwide back to their home television stations | DVB-S2 |
5,531 | DVB-S2X is an extension of DVB-S2 satellite digital broadcasting standard.
DVB-S2X is a digital satellite television broadcast standard. It has been standardized by DVB Project in March 2014 as an optional extension of DVB-S2 standard | DVB-S2X |
5,532 | DVB-SH ("Digital Video Broadcasting - Satellite services to Handhelds") is a physical layer standard for delivering IP based media content and data to handheld terminals such as mobile phones or PDAs, based on a hybrid satellite/terrestrial downlink and for example a GPRS uplink. The DVB Project published the DVB-SH standard in February 2007. The DVB-SH system was designed for frequencies below 3 GHz, supporting UHF band, L Band or S-band | DVB-SH |
5,533 | An Earth observation satellite or Earth remote sensing satellite is a satellite used or designed for Earth observation (EO) from orbit, including spy satellites and similar ones intended for non-military uses such as environmental monitoring, meteorology, cartography and others. The most common type are Earth imaging satellites, that take satellite images, analogous to aerial photographs; some EO satellites may perform remote sensing without forming pictures, such as in GNSS radio occultation.
The first occurrence of satellite remote sensing can be dated to the launch of the first artificial satellite, Sputnik 1, by the Soviet Union on October 4, 1957 | Earth observation satellite |
5,534 | A feed horn (or feedhorn) is a small horn antenna used to couple a waveguide to e. g. a parabolic dish antenna or offset dish antenna for reception or transmission of microwave | Feed horn |
5,535 | Fixed-satellite service (short: FSS | also: fixed-satellite radiocommunication service) is – according to article 1. 21 of the International Telecommunication Union's (ITU) Radio Regulations (RR) – defined as A radiocommunication service between earth stations at given positions, when one or more satellites are used; the given position may be a specified fixed point or any fixed point within specified areas; in some cases this service includes satellite-to-satellite links, which may also be operated in the inter-satellite service; the fixed-satellite service may also include feeder links for other space radiocommunication services.
Classification
This radiocommunication service is classified in accordance with ITU Radio Regulations (article 1) as follows: Fixed service (article 1 | Fixed-satellite service |
5,536 | A focal cloud is the collection of focal points of an imperfect lens or parabolic reflector whether optical, electrostatic or electromagnetic. This includes parabolic antennas and lens-type reflective antennas of all kinds. The effect is analogous to the circle of confusion in photography | Focal cloud |
5,537 | The footprint of a communications satellite is the ground area that its transponders offer coverage, and determines the satellite dish diameter required to receive each transponder's signal. There is usually a different map for each transponder (or group of transponders), as each may be aimed to cover different areas.
Footprint maps usually show either the estimated minimum satellite dish diameter required or the signal strength in each area measured in dBW | Footprint (satellite) |
5,538 | A geosynchronous orbit (sometimes abbreviated GSO) is an Earth-centered orbit with an orbital period that matches Earth's rotation on its axis, 23 hours, 56 minutes, and 4 seconds (one sidereal day). The synchronization of rotation and orbital period means that, for an observer on Earth's surface, an object in geosynchronous orbit returns to exactly the same position in the sky after a period of one sidereal day. Over the course of a day, the object's position in the sky may remain still or trace out a path, typically in a figure-8 form, whose precise characteristics depend on the orbit's inclination and eccentricity | Geosynchronous orbit |
5,539 | A geosynchronous satellite is a satellite in geosynchronous orbit, with an orbital period the same as the Earth's rotation period. Such a satellite returns to the same position in the sky after each sidereal day, and over the course of a day traces out a path in the sky that is typically some form of analemma. A special case of geosynchronous satellite is the geostationary satellite, which has a geostationary orbit – a circular geosynchronous orbit directly above the Earth's equator | Geosynchronous satellite |
5,540 | A ground station, Earth station, or Earth terminal is a terrestrial radio station designed for extraplanetary telecommunication with spacecraft (constituting part of the ground segment of the spacecraft system), or reception of radio waves from astronomical radio sources. Ground stations may be located either on the surface of the Earth, or in its atmosphere. Earth stations communicate with spacecraft by transmitting and receiving radio waves in the super high frequency (SHF) or extremely high frequency (EHF) bands (e | Ground station |
5,541 | Weather satellite pictures are often broadcast as high-resolution picture transmissions (HRPTs), color high-resolution picture transmissions (CHRPTs) for Chinese weather satellite transmissions, or advanced high-resolution picture transmissions (AHRPTs) for EUMETSAT weather satellite transmissions. HRPT transmissions are available around the world and are available from both polar and geostationary weather satellites. The polar satellites rotate in orbits that allow each location on earth to be covered by the weather satellite twice per day while the geostationary satellites remain in one location at the equator taking weather images of the earth from that location over the equator | High-resolution picture transmission |
5,542 | High-throughput satellite (HTS) is a communications satellite that provides more throughput than a classic FSS satellite (at least twice, though usually by a factor of 20 or more) for the same amount of allocated orbital spectrum, thus significantly reducing cost-per-bit. ViaSat-1 and EchoStar XVII (also known as Jupiter-1) do provide more than 100 Gbit/s of capacity, which is more than 100 times the capacity offered by a conventional FSS satellite. When it was launched in October 2011 ViaSat-1 had more capacity (140 Gbit/s) than all other commercial communications satellites over North America combined | High-throughput satellite |
5,543 | A highly elliptical orbit (HEO) is an elliptic orbit with high eccentricity, usually referring to one around Earth. Examples of inclined HEO orbits include Molniya orbits, named after the Molniya Soviet communication satellites which used them, and Tundra orbits.
Such extremely elongated orbits have the advantage of long dwell times at a point in the sky during the approach to, and descent from, apogee | Highly elliptical orbit |
5,544 | The IEEE K-band is a portion of the radio spectrum in the microwave range of frequencies from 18 to 27-Gigahertz (GHz). The range of frequencies in the center of the K-band between 18- and 26. 5-GHz is absorbed by water vapor in the atmosphere due to its resonance peak at 22 | K band (IEEE) |
5,545 | The NATO K band is the obsolete designation given to the radio frequencies from 20 to 40 GHz (equivalent to wavelengths between 1. 5 and 0. 75 cm) during the cold war period | K band (NATO) |
5,546 | The Ka band (pronounced as either "kay-ay band" or "ka band") is a portion of the microwave part of the electromagnetic spectrum defined as frequencies in the range 26. 5–40 gigahertz (GHz), i. e | Ka band |
5,547 | The Ku band () is the portion of the electromagnetic spectrum in the microwave range of frequencies from 12 to 18 gigahertz (GHz). The symbol is short for "K-under" (originally German: Kurz-unten), because it is the lower part of the original NATO K band, which was split into three bands (Ku, K, and Ka) because of the presence of the atmospheric water vapor resonance peak at 22. 24 GHz, (1 | Ku band |
5,548 | The L band is the Institute of Electrical and Electronics Engineers (IEEE) designation for the range of frequencies in the radio spectrum from 1 to 2 gigahertz (GHz). This is at the top end of the ultra high frequency (UHF) band, at the lower end of the microwave range.
Applications
Mobile service
In Europe, the Electronic Communications Committee (ECC) of the European Conference of Postal and Telecommunications Administrations (CEPT) has harmonized part of the L band (1452–1492 MHz), allowing individual countries to adopt this spectrum for terrestrial mobile/fixed communications networks supplemental downlink (MFCN SDL) | L band |
5,549 | A low-noise block downconverter (LNB) is the receiving device mounted on satellite dishes used for satellite TV reception, which collects the radio waves from the dish and converts them to a signal which is sent through a cable to the receiver inside the building. Also called a low-noise block, low-noise converter (LNC), or even low-noise downconverter (LND), the device is sometimes inaccurately called a low-noise amplifier (LNA). The LNB is a combination of low-noise amplifier, frequency mixer, local oscillator and intermediate frequency (IF) amplifier | Low-noise block downconverter |
5,550 | The low-rate picture transmission (LRPT) is a digital transmission system, intended to deliver images and data from an orbital weather satellite directly to end users via a VHF radio signal. It is used aboard polar-orbiting, near-Earth weather satellite programs such as MetOp and NPOESS.
Purpose
LRPT provides three image channels at full sensor resolution (10-bit, 1 km/pixel, six lines/second) in addition to data from other sensors, such as atmospheric sounders and GPS positioning information | Low-rate picture transmission |
5,551 | A weather satellite or meteorological satellite is a type of Earth observation satellite that is primarily used to monitor the weather and climate of the Earth. Satellites can be polar orbiting (covering the entire Earth asynchronously), or geostationary (hovering over the same spot on the equator). While primarily used to detect the development and movement of storm systems and other cloud patterns, meteorological satellites can also detect other phenomena such as city lights, fires, effects of pollution, auroras, sand and dust storms, snow cover, ice mapping, boundaries of ocean currents, and energy flows | Weather satellite |
5,552 | In audio engineering, a mix-minus or clean feed is a particular setup of a mixing console or matrix mixer, such that an output of the mixer contains everything except a designated input. Mix-minus is often used to prevent echoes or feedback in broadcast or sound reinforcement systems.
Examples
A common situation in which a mix-minus is used is when a telephone hybrid is connected to a console, usually at a radio station | Mix-minus |
5,553 | A Molniya orbit (Russian: Молния, IPA: [ˈmolnʲɪjə] (listen), "Lightning") is a type of satellite orbit designed to provide communications and remote sensing coverage over high latitudes. It is a highly elliptical orbit with an inclination of 63. 4 degrees, an argument of perigee of 270 degrees, and an orbital period of approximately half a sidereal day | Molniya orbit |
5,554 | Low-noise block downconverters (LNBs) are electronic devices coupled to satellite dishes for TV reception or general telecommunication that convert electromagnetic waves into digital signals that can be used to transform information into human or machine interpretable data, e. g. , optical images, video, code, communications, etc | Monoblock LNB |
5,555 | An offset dish antenna or off-axis dish antenna is a type of parabolic antenna. It is so called because the antenna feed is offset to the side of the reflector, in contrast to the common "front-feed" parabolic antenna where the feed antenna is suspended in front of the dish, on its axis. As in a front-fed parabolic dish, the feed is located at the focal point of the reflector, but the reflector is an asymmetric segment of a paraboloid, so the focus is located to the side | Offset dish antenna |
5,556 | An orthomode transducer (OMT) is a waveguide component that is commonly referred to as a polarisation duplexer. Orthomode is a contraction of orthogonal mode. Orthomode transducers serve either to combine or to separate two orthogonally polarized microwave signal paths | Orthomode transducer |
5,557 | A parabolic antenna is an antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves. The most common form is shaped like a dish and is popularly called a dish antenna or parabolic dish. The main advantage of a parabolic antenna is that it has high directivity | Parabolic antenna |
5,558 | A polar mount is a movable mount for satellite dishes that allows the dish to be pointed at many geostationary satellites by slewing around one axis. It works by having its slewing axis parallel, or almost parallel, to the Earth's polar axis so that the attached dish can follow, approximately, the geostationary orbit, which lies in the plane of the Earth's equator.
Description
Polar mounts are popular with home television receive-only (TVRO) satellite systems where they can be used to access the TV signals from many different geostationary satellites | Polar mount |
5,559 | The Q band is a range of frequencies contained in the microwave region of the electromagnetic spectrum. Common usage places this range between 33 and 50 GHz, but may vary depending on the source using the term. The foregoing range corresponds to the recommended frequency band of operation of WR22 waveguides | Q band |
5,560 | Rain fade refers primarily to the absorption of a microwave radio frequency (RF) signal by atmospheric rain, snow, or ice, and losses which are especially prevalent at frequencies above 11 GHz. It also refers to the degradation of a signal caused by the electromagnetic interference of the leading edge of a storm front. Rain fade can be caused by precipitation at the uplink or downlink location | Rain fade |
5,561 | An antenna reflector is a device that reflects electromagnetic waves. Antenna reflectors can exist as a standalone device for redirecting radio frequency (RF) energy, or can be integrated as part of an antenna assembly.
Standalone reflectors
The function of a standalone reflector is to redirect electromagnetic (EM) energy, generally in the radio wavelength range of the electromagnetic spectrum | Reflector (antenna) |
5,562 | The S band is a designation by the Institute of Electrical and Electronics Engineers (IEEE) for a part of the microwave band of the electromagnetic spectrum covering frequencies from 2 to 4 gigahertz (GHz). Thus it crosses the conventional boundary between the UHF and SHF bands at 3. 0 GHz | S band |
5,563 | SAT>IP (or Sat-IP) specifies an IP-based client–server communication protocol for a TV gateway in which SAT>IP servers, connected to one or more DVB broadcast sources, send the program selected and requested by an SAT>IP client over an IP-based local area network in either unicast for the one requesting client or multicast in one datastream for several SAT>IP clients. While the system, originating from the DBS satellite operator SES, is originally geared towards receiving and distributing satellite broadcasts in DVB-S or DVB-S2 encoding, SAT>IP also specifies formats for the SAT>IP client request to specify programs broadcast via DVB-C: AppendixD and DVB-T. : AppendixC Only the SAT>IP servers need tuning hardware and software specific to the DVB-broadcast system(s) being used; SAT>IP clients can be any IP-enabled client multimedia device – Tablets, PCs, laptops, Smartphones, “connected” TVs, video game consoles, media players or others | Sat-IP |
5,564 | The Satellite Broadcasting and Communications Association (SBCA) is the national trade organization representing the consumer satellite (direct broadcast satellite) industry in the United States, including the two largest service providers, DirecTV and DISH Network, manufacturers, installers, and distributors of satellite equipment.
Background
Its representatives intervene legally and legislatively against taxes, fees, and ordinances that would restrict the installation and use of satellite antennas. For example, it threatened a lawsuit to defeat an ordinance in Omaha, Nebraska that would have required a fee for satellite dish inspections | Satellite Broadcasting and Communications Association |
5,565 | A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. Communications satellites are used for television, telephone, radio, internet, and military applications. Many communications satellites are in geostationary orbit 22,300 miles (35,900 km) above the equator, so that the satellite appears stationary at the same point in the sky; therefore the satellite dish antennas of ground stations can be aimed permanently at that spot and do not have to move to track the satellite | Communications satellite |
5,566 | A satellite dish is a dish-shaped type of parabolic antenna designed to receive or transmit information by radio waves to or from a communication satellite. The term most commonly means a dish which receives direct-broadcast satellite television from a direct broadcast satellite in geostationary orbit.
History
Parabolic antennas referred to as "dish" antennas had been in use long before satellite television | Satellite dish |
5,567 | A satellite dish is a dish-shaped type of parabolic antenna designed to receive or transmit information by radio waves to or from a communication satellite. The term most commonly means a dish which receives direct-broadcast satellite television from a direct broadcast satellite in geostationary orbit.
History
Parabolic antennas referred to as "dish" antennas had been in use long before satellite television | Satellite dish |
5,568 | A satellite modem or satmodem is a modem used to establish data transfers using a communications satellite as a relay. A satellite modem's main function is to transform an input bitstream to a radio signal and vice versa.
There are some devices that include only a demodulator (and no modulator, thus only allowing data to be downloaded by satellite) that are also referred to as "satellite modems | Satellite modem |
5,569 | In telecommunications, a scrambler is a device that transposes or inverts signals or otherwise encodes a message at the sender's side to make the message unintelligible at a receiver not equipped with an appropriately set descrambling device. Whereas encryption usually refers to operations carried out in the digital domain, scrambling usually refers to operations carried out in the analog domain. Scrambling is accomplished by the addition of components to the original signal or the changing of some important component of the original signal in order to make extraction of the original signal difficult | Scrambler |
5,570 | A set-top box (STB), also colloquially known as a cable box or receiver and historically television decoder, is an information appliance device that generally contains a TV-tuner input and displays output to a television set and an external source of signal, turning the source signal into content in a form that can then be displayed on the television screen or other display device. They are used in cable television, satellite television, and over-the-air television systems as well as other uses.
According to the Los Angeles Times, the cost to a cable provider in the United States for a set-top box is between $150 for a basic box to $250 for a more sophisticated box | Set-top box |
5,571 | Solar conjunction generally occurs when a planet or other Solar System object is on the opposite side of the Sun from the Earth. From an Earth reference, the Sun will pass between the Earth and the object. Communication with any spacecraft in solar conjunction will be severely limited due to the Sun's interference on radio transmissions from the spacecraft | Solar conjunction |
5,572 | In astronomy, a solar transit is a movement of any object passing between the Sun and the Earth. This includes the planets Mercucry and Venus (see Transit of Mercury and Transit of Venus). A solar eclipse is also a solar transit of the Moon, but technically only if it does not cover the entire disc of the Sun (an annular eclipse), as "transit" counts only objects that are smaller than what they are passing in front of | Solar transit |
5,573 | The space segment of an artificial satellite system is one of its three operational components (the others being the user and ground segments). It comprises the satellite or satellite constellation and the uplink and downlink satellite links. The overall design of the payload, satellite, ground segment, and end-to-end system is a complex task | Space segment |
5,574 | Sparklies is a form of interference on analogue satellite television transmissions.
Sparklies are black or white 'hard' interference dots (as opposed to the 'soft' interference patterns of terrestrial television), caused either by too weak or too strong a signal. When within the satellite's rated reception footprint, sparklies are most likely to be caused by a misaligned dish, or LNBs which are too high- or too low-gain for the dish and receiver | Sparklies |
5,575 | Speedcast is a company specializing in communications satellite technology. According to their website, they claim to have "more satellite capacity than any other service provider (C, Ka, Ku, X, L) combined with an extensive multi-technology terrestrial and offshore network (fiber, LTE, microwave). " Speedcast has grown through organic and inorganic growth to be one of the major satellite service providers in the Asia-Pacific, Middle East, Europe, and Africa regions; with a global maritime network serving customers worldwide | Speedcast |
5,576 | A Sun outage, Sun transit, or Sun fade is an interruption in or distortion of geostationary satellite signals caused by interference (background noise) of the Sun when it falls directly behind a satellite which an Earth station is trying to receive data from or transmit data to. It usually occurs briefly to such satellites twice per year and such earth stations install temporary or permanent guards to their receiving systems to prevent equipment damage.
Sun outages occur before the March equinox (in February and March) and after the September equinox (in September and October) for the Northern Hemisphere, and occur after the March equinox and before the September equinox for the Southern Hemisphere | Sun outage |
5,577 | A communications satellite's transponder is the series of interconnected units that form a communications channel between the receiving and the transmitting antennas. It is mainly used in satellite communication to transfer the received signals.
A transponder is typically composed of:
an input band-limiting device (an input band-pass filter),
an input low-noise amplifier (LNA), designed to amplify the signals received from the Earth station (normally very weak, because of the large distances involved),
a frequency translator (normally composed of an oscillator and a frequency mixer) used to convert the frequency of the received signal to the frequency required for the transmitted signal,
an output band-pass filter,
a power amplifier (this can be a traveling-wave tube or a solid-state amplifier) | Transponder (satellite communications) |
5,578 | A Tundra orbit (Russian: орбита «Тундра») is a highly elliptical geosynchronous orbit with a high inclination (approximately 63. 4°), an orbital period of one sidereal day, and a typical eccentricity between 0. 2 and 0 | Tundra orbit |
5,579 | Universal Satellites Automatic Location System (USALS), also known (unofficially) as DiSEqC 1. 3, Go X or Go to XX is a satellite dish motor protocol that automatically creates a list of available satellite positions in a motorised satellite dish setup. It is used in conjunction with the DiSEqC 1 | Universal Satellites Automatic Location System |
5,580 | In a telecommunications network, a link is a communication channel that connects two or more devices for the purpose of data transmission. The link may be a dedicated physical link or a virtual circuit that uses one or more physical links or shares a physical link with other telecommunications links.
A telecommunications link is generally based on one of several types of information transmission paths such as those provided by communication satellites, terrestrial radio communications infrastructure and computer networks to connect two or more points | Telecommunications link |
5,581 | Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing signals, such as sound, images, potential fields, seismic signals, altimetry processing, and scientific measurements. Signal processing techniques are used to optimize transmissions, digital storage efficiency, correcting distorted signals, subjective video quality and to also detect or pinpoint components of interest in a measured signal.
History
According to Alan V | Signal processing |
5,582 | An adaptive beamformer is a system that performs adaptive spatial signal processing with an array of transmitters or receivers. The signals are combined in a manner which increases the signal strength to/from a chosen direction. Signals to/from other directions are combined in a benign or destructive manner, resulting in degradation of the signal to/from the undesired direction | Adaptive beamformer |
5,583 | Adjacent Channel Power Ratio (ACPR) is ratio between the total power of adjacent channel (intermodulation signal) to the main channel's power (useful signal).
Ratio
The ratio between the total power adjacent channel (intermodulation signal) to the main channel's power (useful signal). There are two ways of measuring ACPR | Adjacent channel power ratio |
5,584 | Algebraic signal processing (ASP) is an emerging area of theoretical signal processing (SP). In the algebraic theory of signal processing, a set of filters is treated as an (abstract) algebra, a set of signals is treated as a module or vector space, and convolution is treated as an algebra representation. The advantage of algebraic signal processing is its generality and portability | Algebraic signal processing |
5,585 | In signal processing and related disciplines, aliasing is the overlapping of frequency components resulting from a sample rate below the Nyquist frequency. This overlap results in distortion or artifacts when the signal is reconstructed from samples which causes the reconstructed signal to differ from the original continuous signal.
Aliasing that occurs in signals sampled in time, for instance in digital audio or the stroboscopic effect, is referred to as temporal aliasing | Aliasing |
5,586 | An alpha beta filter (also called alpha-beta filter, f-g filter or g-h filter) is a simplified form of observer for estimation, data smoothing and control applications. It is closely related to Kalman filters and to linear state observers used in control theory. Its principal advantage is that it does not require a detailed system model | Alpha beta filter |
5,587 | In pulsed radar and sonar signal processing, an ambiguity function is a two-dimensional function of propagation delay
τ
{\displaystyle \tau }
and Doppler frequency
f
{\displaystyle f}
,
χ
(
τ
,
f
)
{\displaystyle \chi (\tau ,f)}
. It represents the distortion of a returned pulse due to the receiver matched filter (commonly, but not exclusively, used in pulse compression radar) of the return from a moving target. The ambiguity function is defined by the properties of the pulse and of the filter, and not any particular target scenario | Ambiguity function |
5,588 | Analog signal processing is a type of signal processing conducted on continuous analog signals by some analog means (as opposed to the discrete digital signal processing where the signal processing is carried out by a digital process). "Analog" indicates something that is mathematically represented as a set of continuous values. This differs from "digital" which uses a series of discrete quantities to represent signal | Analog signal processing |
5,589 | In mathematics and signal processing, an analytic signal is a complex-valued function that has no negative frequency components. The real and imaginary parts of an analytic signal are real-valued functions related to each other by the Hilbert transform.
The analytic representation of a real-valued function is an analytic signal, comprising the original function and its Hilbert transform | Analytic signal |
5,590 | The angle of arrival (AoA) of a signal is the direction from which the signal (e. g. radio, optical or acoustic) is received | Angle of arrival |
5,591 | In signal processing, apodization (from Greek "removing the foot") is the modification of the shape of a mathematical function. The function may represent an electrical signal, an optical transmission, or a mechanical structure. In optics, it is primarily used to remove Airy disks caused by diffraction around an intensity peak, improving the focus | Apodization |
5,592 | In mathematics (particularly in complex analysis), the argument of a complex number z, denoted arg(z), is the angle between the positive real axis and the line joining the origin and z, represented as a point in the complex plane, shown as
φ
{\displaystyle \varphi }
in Figure 1.
It is a multivalued function operating on the nonzero complex numbers.
To define a single-valued function, the principal value of the argument (sometimes denoted Arg z) is used | Argument (complex analysis) |
5,593 | The asymptotic gain model (also known as the Rosenstark method) is a representation of the gain of negative feedback amplifiers given by the asymptotic gain relation:
G
=
G
∞
(
T
T
+
1
)
+
G
0
(
1
T
+
1
)
,
{\displaystyle G=G_{\infty }\left({\frac {T}{T+1}}\right)+G_{0}\left({\frac {1}{T+1}}\right)\ ,}
where
T
{\displaystyle T}
is the return ratio with the input source disabled (equal to the negative of the loop gain in the case of a single-loop system composed of unilateral blocks), G∞ is the asymptotic gain and G0 is the direct transmission term. This form for the gain can provide intuitive insight into the circuit and often is easier to derive than a direct attack on the gain.
Figure 1 shows a block diagram that leads to the asymptotic gain expression | Asymptotic gain model |
5,594 | Audio signal processing is a subfield of signal processing that is concerned with the electronic manipulation of audio signals. Audio signals are electronic representations of sound waves—longitudinal waves which travel through air, consisting of compressions and rarefactions. The energy contained in audio signals or sound level is typically measured in decibels | Audio signal processing |
5,595 | Autocorrelation, sometimes known as serial correlation in the discrete time case, is the correlation of a signal with a delayed copy of itself as a function of delay. Informally, it is the similarity between observations of a random variable as a function of the time lag between them. The analysis of autocorrelation is a mathematical tool for finding repeating patterns, such as the presence of a periodic signal obscured by noise, or identifying the missing fundamental frequency in a signal implied by its harmonic frequencies | Autocorrelation |
5,596 | The autocorrelation technique is a method for estimating the dominating frequency in a complex signal, as well as its variance. Specifically, it calculates the first two moments of the power spectrum, namely the mean and variance. It is also known as the pulse-pair algorithm in radar theory | Autocorrelation technique |
5,597 | A real time interferometric autocorrelator is an electronic tool used to examine the autocorrelation of, among other things, optical beam intensity and spectral components through examination of variable beam path differences. See Optical autocorrelation.
Description
In an interferometric autocorrelator, the input beam is split into a fixed path beam and a variable path beam using a standard beamsplitter | Autocorrelator |
5,598 | Automated ECG interpretation is the use of artificial intelligence and pattern recognition software and knowledge bases to carry out automatically the interpretation, test reporting, and computer-aided diagnosis of electrocardiogram tracings obtained usually from a patient.
History
The first automated ECG programs were developed in the 1970s, when digital ECG machines became possible by third-generation digital signal processing boards. Commercial models, such as those developed by Hewlett-Packard, incorporated these programs into clinically used devices | Automated ECG interpretation |
5,599 | Automatic Link Establishment, commonly known as ALE, is the worldwide de facto standard for digitally initiating and sustaining HF radio communications. ALE is a feature in an HF communications radio transceiver system that enables the radio station to make contact, or initiate a circuit, between itself and another HF radio station or network of stations. The purpose is to provide a reliable rapid method of calling and connecting during constantly changing HF ionospheric propagation, reception interference, and shared spectrum use of busy or congested HF channels | Automatic link establishment |
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